With regard to the DC/DC converter as described above, the DC/DC converter disclosed in PLT 1 described below is known. In the technology of PLT 1, across a transformer, the first converter of full bridge circuit is provided in the first DC power source side, and the second converter of full bridge circuit is provided in the second DC power source side. The first reactor is provided between the first winding of the transformer and the first converter, and the second reactor is provided between the second winding of the transformer and the second converter.
When a voltage of the first DC power source or the second DC power source is higher than a voltage generated in the first winding or the second winding of the transformer, that is, when the step-up operation is necessary, the step-up operation is performed using the first reactor or the second reactor; and on the other hand, when the step-down operation is necessary, the step-up operation is not performed. Therefore, in the technology of PLT 1, total four operation modes are switched according to the output DUTY ratio which represents the transmission power amount. The four operation modes consist of an operation mode for performing the step-up operation (step-up charge) and a operation mode for performing the step-down operation (step-down charge) in the first power transmission (charge of the second DC power source) which transmits electric power to the second DC power source from the first DC power source, and an operation mode for performing the step-up operation (step-up discharge) and a operation mode for performing the step-down operation (step-down discharge) in the second power transmission (discharge of the second DC power source) which transmits electric power to the first DC power source from the second DC power source.
Specifically, in the technology of PLT 1, as shown in FIG. 28 of PLT 1, the phase shift amounts θ1, θ2, θ3, θ4, which are the relative phases of the on-off driving signal of each switching device, are changed according to the output DUTY ratio.